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Permeable Pavement Systems T-10
infiltration or permeability testing. Selection of the section type should be based on careful
assessment of the subsurface exploration and testing data.
2. Required Storage Volume: Provide the WQCV based on a 12-hour drain time.
• Find the required WQCV (watershed inches of runoff). Using the effective impervious area of
the watershed area, use Figure 3-2 located in Chapter 3 to determine the WQCV based on a 12-
hour drain time. The maximum recommended ratio for tributary impervious area to permeable
pavement area is 2.0. Higher loading is not recommended, as it may increase the required
maintenance interval.
• Calculate the design volume as follows:
Where:
V = WQCV
12 A Equation PPS-1
A = watershed area tributary to the permeable pavement (ft 2 )
V = design volume (ft 3 )
• Add flood control volume if desired. When designing for flood control volumes, provide an
overflow that will convey runoff in excess of the WQCV directly into the reservoir. A gravel
strip or inlet that is connected to the reservoir can provide this overflow.
August 2013 Urban Drainage and Flood Control District PPS-5
Urban Storm Drainage Criteria Manual Volume 3